Launch and recovery system for unmanned aerial vehicles

ABSTRACT

A method of launching and retrieving a UAV (Unmanned Aerial Vehicle) ( 10 ). The preferred method of launch involves carrying the UAV ( 10 ) up to altitude using a parasail ( 8 ) similar to that used to carry tourists aloft. The UAV is dropped and picks up enough airspeed in the dive to perform a pull-up into level controlled flight. The preferred method of recovery is for the UAV to fly into and latch onto the parasail tow line ( 4 ) or cables hanging off the tow line and then be winched back down to the boat ( 2 ).

CROSS-REFERENCE TO RELATED APPLICATIONS

This is a divisional application of pending U.S. application Ser. No.10/031,025, which is a national phase application under 35 U.S.C. § 371of PCT application US00/20099, and claims priority of ProvisionalApplication 60/145,286, filed Jul. 23, 1999.

FIELD OF THE INVENTION

The present invention relates to the methods and mechanisms required tolaunch and retrieve aircraft from point locations without the use ofrunways.

BACKGROUND OF THE INVENTION

Previously glider aircraft have been towed aloft and then released tofly off on their own and catapults have been used to rapidly acceleratean aircraft up to flying speed in a short distance. Also aircraft havebeen fitted with tail hooks or other apparatus to try to engagearresting cables or have been flown into nets in order to arrest theirforward movement in a short distance.

Prior art U.S. Pat. No. 4,753,400 (Reuter, et al.) comes closest to oneof the preferred embodiments of the proposed invention. However thisprior art discloses a very complicated system with a launching parachuteand parachute retainer that gets jettisoned for each recovery cyclewhich in turn launches a ram-air parachute which holds up a ribbonparachute which acts to capture the UAV. A ship mounted stanchion, netand rotating cradle is then required to disentangle the UAV from theribbon parachute. In this prior art the UAV engaged the ribbon parachutejust below the supporting ram-air parachute with very little arrestmentdistance and thus very high loads. In this prior art the UAV approachesin the turbulent, blocked flow from the ribbon parachute and the ribbonparachute also causes a very large amount of unnecessary drag for thesystem.

There is also another problem with this prior art. Not only is there noapparent mechanism for retaining the UAV after it impacts the ribbonparachute but it would appear that the UAV would tend to bounce off andtend to drop from the ribbon parachute. Current state-of-the-art UAVlaunch and arrestment systems are bulky and difficult to integrate ontosmaller ships and are time-consuming to operate, erect and tear down. Inaddition the recovery is very sensitive to sea states and ship motionand very often results in damage to the UAV and arrestment system. Therecovery also requires significant piloting skills since the UAV musthit the center of the arrestment net in close proximity to the water,ship structure and personnel while traveling at relatively high speedsthrough the turbulent air wake from the ship.

SUMMARY OF THE INVENTION

The present invention provides improvements in the launch and recoveryof aircraft from a point location without the need for runways. Thepreferred method of launch involves carrying the UAV up to altitudeusing a parasail similar to that used to carry tourists aloft. The UAVis dropped and picks up enough airspeed in the dive to perform a pull-upinto level controlled flight.

The preferred method of recovery is for the UAV to fly into and latchonto the parasail tow line or secondary cables hanging from the parasailtow line and then be winched back down to the boat. Although notpreferred, a net capturing device for use with a parasailing rig isdisclosed. For land use a lighter than air suspended tethered parachuteor a tethered tip drive rotor replaces the parasailing rig.

The proposed system is designed to avoid the previously describedproblems and also allow launch and recovery of UAVs from vessels down toas small as 25 feet long. The proposed system also offers the potentialfor other uses such as local area surveillance when no UAVs areoperating near by, airborne decoys or antennas for intelligence orcommunications, and the like, by using the parasailing system by itselfas an airborne platform.

This new launch and arrestment technique takes advantage of modern lowcost commercial parasailing technology that is proven, safe, man-ratedand can raise and lower passengers directly from the back of a smallboat.

For launch the UAV is carried aloft in place of a passenger and releasedat altitude. The UAV picks up airspeed as it dives and the pilot pullsback on the control stick so the UAV will pull up into level flight.This technique has already been demonstrated. The release mechanismholds the UAV upright and facing forward into the relative wind.

For recovery the UAV engages the cable approximately half way betweenthe ship and the parasail by deflecting the cable into a latching hookmechanism. The UAV is then reeled back in.

The resulting launch and recovery approach has the followingcharacteristics;

-   A) Safer, less sensitive to sea states and requires less pilot    training.    -   Launch and recovery is performed at a safe altitude away from        the water, ship and ship's personnel and if the UAV misses the        cable it simply goes around for another attempt.    -   The UAV's forward looking camera can be used for accurate        guidance into the cable. The UAV avoids having to fly through        the turbulent wake of the ship and is relatively unaffected by        the pitching, rolling and heaving of the ship in higher sea        states.-   B) Less potential for damage.

This system arrests the UAV over a greater distance than a conventionalnet system resulting in lower loads and the loads are applied at knownUAV hardpoints. Arrestment loads are inversely proportional to thearrestment distance so that stopping a UAV in 100 feet takes only 10percent of the loads of stopping it in 10 feet. The launch loads are, ofcourse, dramatically reduced also. The potential of the UAV impactingthe ship or water is greatly reduced.

-   C) More compact, easier to deploy, store and operate.    -   The proposed system is compact enough to be used on 25 foot long        parasailing boats. Deploying the system consists of running two        of the parachute risers up a 10 foot flagpole or manually        holding open the mouth of the parachute which causes the chute        to fill with air and the parachute is reeled out. To store the        system, the parachute is reeled back in and the two upper risers        are pulled down to deflate the chute. The parachute need not be        carefully folded and typically the risers are chain knotted and        then the chute is stuffed in a bag.    -   Unlike a net system the UAV after arrestment doesn't need to be        disentangled from a net.

It is an object of the invention to provide a simple, compact,inexpensive, lightweight and safer method of launching and retrievingconventional fixed wing aircraft from a point location.

It is a further object of the invention to get the arrestment mechanismup above any objects the UAV might otherwise run into and above anyturbulent air from objects near the water or ground such as the ship'ssuperstructure, trees, etc.

It is an object of the invention to have an aircraft flight path thatdoesn't pass over the recovery ship to eliminate the potential that theaircraft might not firmly engage the recovery system yet be disturbedand crash land on the ship.

It is an additional objective of the invention to provide a launch andrecovery system that exerts lower loads and inflicts less damage to theUAV and arrestment system.

It is an additional objective of the invention to provide an arrestmentsystem that is less effected by heavy seas and the pitching, heaving androlling of the recovery ship.

It is an object of the invention to have an arrestment system that usesa parasail.

It is a further object of the invention to provide improvements toparasails to improve their stability, reduce required ballast, and easelaunch and recovery and deck handling.

It is an object of the invention to provide an arrestment system thatachieves a firm latched engagement and is easier to disengage the UAVfrom the arrestment system after recovery.

It is an objective of the invention to provide a launch and arrestmentsystem that can also provide other functions such as carrying sensors orantennas aloft for local area surveillance, communications, electronicintelligence or warfare or for getting steerable parachutes aloft thatcan be released for pilot parachute training or delivery missions.

It is a further object of the invention to utilize normal aircraftstructure such as wings, fuselages and propeller guards or wiresattached to these structures to guide the arrestment cable intoengagement with a latching hook mechanism.

It is a further object of the invention to have a recovery system thatcan recover aircraft at a higher altitude to avoid ground fog or a loweraltitude to be under the cloud cover.

It is another object of the invention to have a launch and recoverysystem that raises and lowers the aircraft in a level attitude forexample for easy transfer on and off of its landing gear.

DESCRIPTION OF THE DRAWINGS

FIG. 1 is a side view of one embodiment of the invention showing thelaunch approach.

FIG. 2 is an isometric close up view of an alternative launchconfiguration.

FIG. 3 is a plan view looking down on an unmanned aircraft designed tobe launched and retrieved with this invention. A portion of the releasemechanism used for launch is also shown.

FIG. 4 is a view in side elevation taken along lines 4-4 in FIG. 3.

FIG. 5 is a side view of one embodiment of the invention showingdifferent arrestment approaches.

FIG. 6 is a view of an alternative way to attach recovery lines to theparasail tow line.

FIG. 7 is a view of an alternative way to attach recovery lines to theparasail tow line.

FIG. 8 is a top plan view of FIG. 5.

FIGS. 9-12 are plan views of some other aircraft configurations for thisinvention.

FIG. 13 is an enlarged view of the hook mechanism on the aircraft inFIG. 12.

FIGS. 14A and 14B are frontal views of additional aircraftconfigurations for this invention.

FIG. 15 is a side view of the aircraft equipped with a grappling hookfor the parasail tow line.

FIG. 16 is a view of the aircraft equipped with a grappling hook andsuspension harness.

FIG. 17 is an isometric view of a net system attached to the parasailtow line designed to capture an aircraft.

FIGS. 18-20 show successive views of the net system in FIG. 17 justafter capturing a UAV.

FIG. 21 is an example of how this arrestment approach can be performedwithout a parasail holding up the arrestment lines by instead usingcables strung between two poles.

FIG. 22 is a means of launching and retrieving UAVs with a helicopter.

FIG. 23 shows a mechanism for holding the UAV level by attaching at arigid point well above the center of gravity.

FIG. 24 is a variation on the invention for recovery of UAVs on land.

FIGS. 25A, 25B, and 25C show other embodiments of deployable liftingsystems.

FIG. 26 shows a tow line hook mechanism.

FIG. 27 is a view of an alternate embodiment of the invention featuringa rotating arm on the back of a ship for suspending arrestment lines.

FIG. 28 is a view from the rear of a ship in which the rotating arm isswung away from the ship.

FIG. 29 is a view of an alternate embodiment of the invention in whichthe arrestment line is suspended from an elastic line for decreasing thearrestment load placed on the aircraft during recovery.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Launch-Preferred

Referring now by reference numerals to the drawings and first to FIG. 1one of the preferred embodiments comprises a boat 2, a tow line 4, winch6, parachute 8, plastic barrel of water as a ballast weight 9, unmannedaerial vehicle (UAV) 10 and release mechanism 12. The launch procedurestarts by inflating the parachute 8 which can be done by raising itsrisers with a pole designed for this purpose which is well known in theart or by having persons hold up the separated riser bundles until thechute inflates in the wind. Because conventional parasailing parachutesneed a weight hanging under them to keep them oriented properly afterthe UAV has been released, a barrel of water 9 or other weight isattached where a tourist would normally be attached to go upparasailing. Use of such a water ballast is well known in the art as amethod used for training people to operate parasailing equipment. Therelease mechanism and structure 12 can be integrated onto the bottom ofthe ballast 9 or can be detachable from it. It also can be made heavyenough so as not to require additional ballast for the parasail. Thealternative is to have a steerable type parasail with a remote controlunit pulling the control lines in place of a paratrooper to keep theparasail oriented upright so it is generating lift vertically.

For launch, the parasail is inflated first and then the ballast 9,release structure 12 and UAV 10 are combined and can either be raised sothat straps 300 can be attached to the parasail harness in theconventional manner or the parasail harness can be pulled down to attachto the straps 300 as shown in FIG. 1. The straps 300 can also beattached when the parasail harness attach points on the left and rightriser bundles are low enough to reach the straps 300 from the waterbarrel ballast 9 as is known in the art and then the system is raisedinto the air when the parasail is reeled out with the winch. With thislater approach care may need to be taken to avoid excess swinging of theUAV and potential propeller contact with the deck. Engine run-ups can beperformed on the deck before launch or after being attached to the line,but for the later approach it may be desirable to have a thrust link 15such as shown in FIG. 2 if for example the aircraft has a tractorpropeller without a propeller guard so that the propeller won't contactthe tow line 4.

The winch 6 then reels the parachute out until the UAV has reachedsufficient altitude for a launch. It should be understood that therelease structure can hold the UAV in a somewhat nose up attitude so theUAV's wings are also generating lift to assist in raising the combinedsystem and it should also be understood that the UAV's propulsive systemcould also assist for example if it's a vectored thrust vehicle like theHarrier or if the UAV is held in a nose up attitude by the releasemechanism. As the UAV is approaching launch altitude the remote pilotcan verify the proper operation of the flight controls by moving theUAV's control surfaces and watching the vehicle respond which isfacilitated by the airflow and some flexibility in the mounting of theUAV.

The engine is placed at idle and a signal is then sent to the releasemechanism 12 either through an electrical line carried by the tow line 4or a radio signal. The mechanism that releases the UAV may consist ofactuator 14 and pin 16 which engages UAV mounted bracket 22 as shown inFIG. 3. UAV 10 is held up only by pin 16 passing through a hole inbracket 22 which is part of the UAV but sticks up above the UAVs outermold-line and into a slot provided in the bottom of the releasemechanism structure. For clarity, only the outline of the releasemechanism structure 12 where it bears against the upper surface of theUAV 10 with a circular rubber seal is shown in FIG. 3. The releasestructure 12 will help stabilize the UAV 10 from pitching, rolling andyawing since it bears down on the upper surface of the UAV all aroundthe attach bracket 22 with the rubber seal. It will of course beunderstood that the release mechanism could also be part of the UAV 10as opposed to being attached to the parasail system.

To release the UAV, actuator 14 pulls pin 16 out of UAV mountedstructural bracket 22 allowing the UAV to fall. The UAV picks up speedin a dive, power is applied to the engine and once sufficient airspeedis achieved the pilot pulls back on the control stick so the UAV will doa pull-up into level controlled flight. During this process the pilotperforms a mild turn so the UAV won't fly into the tow line 4.

Although the winch 6 is shown on the highest deck of the ship in FIG. 1it will very often be more advantageous to place the winch 6 on theships flight deck 7. It can be advantageous to launch and retrieve theparachute on the upwind side of the flight deck 7 due to the airturbulence directly behind the ship's superstructure. FIG. 8 shows thepreferred approach to do this where the winch 6 is mounted to the portside of the ship 2. The tow line 4 comes directly out of the winch 6headed across the flight deck 7 toward the starboard side of the ship.The tow line 4 passes through a pulley assembly 11 which incorporates ahook that can be secured to an aircraft tie-down pad on the port side(as shown in solid lines) or the starboard side (as shown in dashedlines) so that it is easy to launch the parachute from the upwind sideof the ship 2 without moving the winch 6 which might be connected to theship's hydraulic system. The pulley assembly 11 preferably will never belocated closer than 6 feet from the winch so as not to put too much sideforce on the level winder.

Launch Alternate

FIG. 2 shows an alternate launch arrangement where the release structure12 connects not to the ballast 9 but to the tow line 4 through rods 13and 15 which by attaching at two points on the tow line can helpstabilize the UAV 10 in yaw and pitch. This arrangement might be betterfor some shipboard installations such as in the situation that it isdifficult to get enough wind on the flight deck 7 to safely launch theUAV 12 due to the blockage of the ship's superstructure or the airturbulence causes the parasail to shake making it more difficult, forexample, to start the aircraft's engine. Under these circumstances theparasail 8 and ballast 9 which weighs a lot less than the UAV 10 can belaunched first and raised above the airflow blockage and turbulence fromthe superstructure in order to get the desired lift to launch the UAV10.

Although the currently used approach to ballast a parasail is to use twoflexible straps 300 to connect a water barrel ballast to the parasailrisers as shown in FIG. 1, there is a better approach. FIG. 2 showsrigid roll stability rods 310, 312 and 314 that replace the currentlyused flexible straps 300 and also attaches the water ballast 9 to thepoint 324 where the parasail attaches to the tow line 4. Also the waterbarrel ballast 9 would be hung lower below the parasail risers than ispresently the practice. These two changes allow a lighter ballast to beused and still achieve the same roll stability levels and also preventsa condition where the parasail can roll over too far and never recover.

Roll stability can best be described by stating that when the rightparasail riser ring 320 gets higher than the left 322, more of theballast weight is carried by ring 320 which causes the parasail to rollback level again. The farther the ballast is below these rings 320, 322the faster the weight gets shifted to the uphill ring. Also there is acondition when a parasail is pulled too fast that it can oscillate sideto side and roll 90 degrees or more so that all the weight is on onering but that ring is on the centerline of the parasail so the weightisn't creating a restoring moment to roll the parasail back level. Withthe proposed configuration the rigid members 310, 312 and 314 wouldcontinue to hold the ballast weight out to the side and thus wouldcontinue to provide roll stability. Also rigid member 314 preventsballast 9 from swinging back and forth excessively during a UAVarrestment.

For the arrestment and recovery, the UAV 10 flies into and latches ontocables suspended below the parasail 8 as shown in FIG. 5. There are manydifferent preferred configurations because the current invention isintended to be useable with all different sizes, configurations andstructural designs of existing aircraft. For example with a small UAVthe wingtip ends up being a good place to put a latching hook to engageone of the cables but larger aircraft do not naturally have enoughstructure at the wingtip to handle the arrestment loads. Putting alatching mechanism on the nose of the aircraft is desirable until theaircraft gets too heavy to manhandle by sailors on the deck and then itis desirable to have the latching mechanism near and preferably abovethe vehicles center of gravity so that it hangs level or can be leveledby hand and lowered onto its landing gear or a ground trolley. Thealternative more man-power intensive approaches are to have a crane thatcan be manually attached to the UAV's release point so as to support andlevel the UAV as it is lowered by the parasail. Alternatively a line orstructural member that is always carried by the UAV 10 can connect adetachable latching hook used in the engagement with a typical parachuteharness or other hardpoint over the vehicles center of gravity forholding the UAV level.

Arrestment-Preferred Approach

For the arrestment, the preferred approach is for the vehicle to flyinto and latch onto a net or multiple lines hanging down from the towline 4 approximately half way between the parasail and the ship and withthe UAV flying at right angles to the direction of travel of the ship asshown by flight path 38 in FIG. 8. The multiple lines make a larger,easier target for the pilot. In order to make sure that the lines do notblow open wide enough to miss the UAV's latching mechanisms the verticallines can be connected with horizontal lines to effectively form a netand/or tension can be created on the lines such as shown with lines 20,21 in FIG. 5 where rope 25 connecting the bottoms of lines 20, 21 can beof relatively large diameter to add some weight and stiffness and/or asmall parachute 53 can provide tension in line 25 and in turn a downloadon lines 20, 21. It is of course understood that the UAV can directlylatch onto the tow line 4. Although not preferred it is of courseunderstood that lines could also hang down directly from the parasail 8.In this latter case the preferred approach would be to have a relativelylong line and the energy would be absorbed by gravity and aerodynamicdrag as the UAV contacts and then swings the line up and then continuesto swing back and forth.

Preferred Flight Path

The preferred flight path of the UAV for engagement is at right anglesto the direction of travel of the ship as shown by arrow 38 in FIG. 8.In this manner a level approach can be used and the arrestment energy isabsorbed primarily by deflecting the tow line to the side. It also makesit the easiest to hang a net or series of vertically hanging lines onthe tow line 4 at right angles to the direction of flight of the UAV 10.It also makes it easier for the UAV pilot to find the arrestment pointif a banner or flag is used since the wind will blow it out at rightangles to his line of sight. Also if the UAV was not properly capturedbut falling out of control it wouldn't land on the ship. The UAV pilotwill generally fly the aircraft into engagement using a forward lookingcamera onboard the aircraft. However if the onboard camera fails, getsfowled by oil or water or whatever a camera 201 and/or 205 can be placedon the tow line or recovery lines above and to the side of the intendedarrestment point as shown in FIG. 6 and looking in the direction of theoncoming aircraft with field of views 203 and 207 to help the pilotsteer the aircraft in. Also the image from these cameras 201 and 205 canbe flipped electronically left to right and right to left before beingdisplayed to the remote pilot so that the pilot can fly the aircraft asif it is flying away from him instead of flying towards him which ismuch more natural. In the configuration shown in FIG. 6 the remote pilotwould fly the aircraft so that it flies directly below camera 201. Itwill be noted that at some point the aircraft passes out of camera 201'sfield of view. Camera 205 can be helpful in better gauging the properheight than using camera 201 by itself and in fact one pilot watchingthe image from camera 205 could concentrate on keeping the aircraft atthe correct altitude while the other pilot looking through camera 201concentrates on keeping it centered left to right. If only camera 201 isutilized then it is advisable, in order to help the pilot best gauge theproper aircraft height and hit the center of the arrestment lines, topaint straight vanishing lines on the pilot's display that trace theideal location of the aircraft's wingtips during the approach as thewingtips get farther and farther apart and lower on the display screen.Cameras to the left and right of the ideal arrestment point and at thecorrect height can also be very effective.

Delta Wing Configuration

In the configuration shown in FIG. 3, the tow line 4 or secondary linessuch as 20, 21 contact the leading edge of the UAV 10 and are deflectedout to the wingtip where they engage a hook 26. A spring loaded latch 28may be positioned at the entry point of hook 26 which deflects out ofthe way and then snaps closed to trap tow line 4 inside hook 26. Thehook 26 may have a forward swept extension 30 on the outboard side thatcould first deflect the cable inboard before engaging the hook 26. For astraight winged aircraft a wire can be strung from the nose of theaircraft, or along the fuselage, to the wingtip to drive the cable outto the hook to simulate the leading edge of a delta wing. Hook 26 may bepermanently attached at the wingtip or may be retained with tape 270that is designed to tear under the load of an engagement. In this latercase, as shown in FIG. 3, the hook 26 would be attached to cable 272which in turn is attached to a three cable harness 274 which attaches tothree or more hard points 276 on the top surface of the aircraft and isalso taped in place until the arrestment loads pull it free. With thisapproach, after the arrestment, the aircraft 10 ends up being suspendedin a level attitude below the harness in the same manner used forparasail deployments.

Hook Retaining

Although it is very desirable to have a latching mechanism which allowsa simple hook design, it is not absolutely mandatory because of thelocation and design of this hook. The center of gravity of the UAV isapproximately at bracket 22 so the arrestment loads and loads to supportthe UAV after arrestment will in general both be continuing to try toforce the tow line 4 into the hook 26 and not trying to pull it out. Inaddition, for example, the force of the arrestment might drive the towline 4 through the throat 24 of the hook even though the line 4 islarger in diameter than the throat 24. This can be done by eithercompressing the line 4 or the temporary enlargement of the throat 24 dueto the arrestment loads causing the hook 26 to flex open. As a resultthe line 4 will not pass back out through the throat 24 without asignificant load being applied. With enough flexibility in hook 26,throat 24 might be totally closed except when the line 4 forces it openin order to pass through. Inner throat 23 might be larger, the same sizeor smaller than outer throat 24 and might essentially have an inner hook27 so it is difficult for the line 4 to find its way out of the hook 26.Also barbs 17 on hook 26 might further restrain the line 4 from exitingthe hook 26. For extremely light micro-UAVs, even Velcro or magnetsmight be strong enough to provide the engaging mechanism in place ofhook 26.

For tractor propeller UAV configurations such as shown in FIGS. 3 and 4,a propeller guard 32 may be used to deflect the line 4 around thepropeller. As an alternative to placing the latching mechanism 26 on thewingtips it can also be placed on the propeller guard as illustrated byhook and latching mechanism 33 in FIG. 3. This adds some weight upforward which helps if the aircraft has an aft center of gravity problemand reduces the need for substantial structure out at the wingtips butthe narrower spacing between the left and right ends of the propellerguard means that the arresting system needs more vertically suspendedlines spaced closer to each other to make sure that at least one linewill be deflected by the propeller guard into engagement with a latchinghook 33. Latching hooks could also be placed on the propeller guard rods29 above or below the propeller to deflect and capture horizontal linesin the net. It is best to deflect lines in the direction of the leastresistance to assure a successful engagement. If a net is hanging fromthe tow line 4 without any devices such as small parachutes or weightsat the bottom of the net to provide tension or a restraint to the bottomof the net then the least direction of resistance is toward the tow line4. If the UAV is using flight path 38 then up and/or to the left towardthe tow line 4 is the preferred direction to deflect the cable. FIG. 4shows a side view of the nose of the aircraft in FIG. 3 and shows howpropeller guard 29 is designed to push a line of the net up and intoengagement with hook 180. After engagement the net will want to pull upand aft relative to the aircraft so hook 180 has a top spike 182 thatprevents the line from going up and forces it to go aft into the mouthof the hook 180.

FIGS. 9-11 show a number of UAV configurations designed to deflect thecable in to the wing root which is very close to the center of gravityand where the structure is naturally very strong. For example, a forwardswept wing will naturally tend to deflect the tow line 4 in toward thewing root area. The UAV configuration in FIG. 10 has a forward sweptwing out to about half span and the configuration in FIG. 11 achievesthe same effect by adding forward pointing rods 34 and wires 36 todeflect the cable into the latching hook at the wing root.Alternatively, a wire from the aircraft's nose to a wingtip could drivethe cable out to a latching mechanism at the tip similar to thatdescribed for delta wing aircraft. For stowage onboard ship it can bedesirable to have a UAV where the wing can be rotated 90 degrees to layflush over the fuselage. For this kind of configuration prior toarrestment, the wing could be rotated up to 45 degrees such as shown inFIG. 9 in order to direct the tow line 4 into a latched engagement bythe wing root. An equivalent forward swept snare arrangement using theside of the fuselage and one of the wings can also be achieved with astraight winged aircraft as shown in FIG. 12. This can be achieved byyawing or side-slipping the vehicle with the rudder prior to engagementand/or by intersecting the tow line 4 by flying perpendicular to thedirection of travel of the parachute and tow line 4 as shown by flightpath arrow 38 in FIG. 8. In the latter approach the movement of the towline 4 in the direction indicated by flight path arrow 40 in FIG. 8provides the same effect as some yawing of the aircraft to help drivethe cable in to the aircraft's wing root area. A front view of a UAV 42in FIG. 5 is shown in a side-slip while on a perpendicular flight pathprior to engagement with tow line 4 at point 60. It can be seen that therolled attitude to achieve the side-slip also places the wings at afavorable more perpendicular angle to the tow line 4 for the largestcapture envelope. The arrestment line configuration that is shown inFIG. 6 also can help drive the arrestment lines 20, 21 into the vehicleswing root area since line 25 will go tight after an engagement and startpulling the bottoms of line 20, 21 to the left toward the aircraft'swing root area. The straight winged aircraft configuration in FIG. 12can also engage a net since the forward fuselage will penetrate througha hole in a net with wide spacings between lines until the net hits thewing and then the load from the engagement will pull the net backagainst the wing and inboard to wrap around and under the fuselage whichwill drive the cables of the net into the left and right wing rootlatching mechanisms shown in FIG. 13.

For many of the configurations such as those described in FIGS. 3, 9, 10and 11, it is desirable to have at least a 15 degree swept back or 20degree swept forward angle on the leading edge of the aircraft's wing orother lateral deflecting structure in order to more reliably deflect thearresting cable to the hook independent of normal aircraft yaw angles.In most of the configurations described so far the UAV is designed todeflect a cable laterally inboard or outboard relative to the UAV andinto engagement with a latching hook. It is also understood that it ispossible to design a UAV to deflect a horizontally strung cablevertically relative to the UAV into a latching hook using, for example,an upper surface hook, a nose 71 or tail hook 70, grappling hook 75 orvertical tail surface latching hook 72 of a UAV 74 as shown in FIG. 15.

Ever since aircraft first tried to snag a horizontal wire strung acrossa flight deck with a tail hook people have tried to use this basicapproach. This approach works well on a flight deck because the deckguides the aircraft and tail hook into engagement with the horizontalcable. However, it is more difficult when a large flight deck is notavailable and the pilot must control the height more precisely and/or alarge vertical deflector must be added to the aircraft which adds weightand drag. One preferred approach to handle this problem is to have asmall nose deflector 71 and latching mechanism designed to engage a netwith multiple horizontally strung lines as part of a net such as shownin FIG. 17.

Another approach is to use a grappling hook 75 on a line 73 attached tothe UAV 74 near its center of gravity as shown in FIG. 15. The UAV 74would preferably fly upside down for the engagement or a portion 77(shown in dashed lines) of the line 73 would be strung around the sideof the fuselage and attached to the top of the UAV 74 over the center ofgravity with or without a typical UAV parachute harness attachment 400,as shown in FIG. 16, so the UAV 74 would hang right side up and levelwhen it is lowered onto the flight deck 7. A release mechanism (notshown) of course could be used so that the grappling hook 75 could beheld in a retracted position for most of the flight and released to hangdown on its cable just prior to an arrestment. An aft view of UAV 74 inFIG. 5 shows how it could engage the tow line 4 with its wings banked atthe same angle as the slope of the tow line 4 and with the UAV 74 in asideslip and approaching the tow line 4 from the side such as flightpath 38 as shown in FIG. 8.

It should be understood that a traveler mechanism consisting of one ormore grappling hooks 79 with latches could also be placed on the towline 4 with the tow line 4 passing up through the centerline of thegrappling hook 79 as shown in FIG. 26. The UAV could be arrested byflying flight path 46 as shown in FIGS. 5 and 8 with aircraft drag line73 sliding up along the side of tow line 4 and into engagement with foursided grappling hook 79. Hook 79 would incorporate an ascender mechanism402 in it which is well known in the art of mountain climbing equipmentthat allows the grappling hook 79 to easily slide up the tow line 4 butnot down. With this system grappling hook 75 could be replaced by just afixed stop.

It is also understood that for example a fixed grappling hook could beplaced on a line hanging below the tow line such as line 25 in FIG. 5but without use of a parachute 53 so that the line 25 is more highlyrestrained at the left point 47 than at the right. The aircraft couldfly a flight path 38 and aircraft drag line 73 could then deflect andslide along line 25 until it engages the grappling hook.

For nose-mounted latching hooks such as 33 and 71 the preferred approachis to use flight path 38 and fly into and engage the ropes of a netsimilar to that shown in FIG. 17. The ropes of the net would be closeenough together that the latching hooks would be assured of engaging oneof the lines. Another approach utilizing a retaining trap is shown byrods 351 on aircraft 124 in FIG. 17 which are spring loaded out but arehinged about their forward end so that they can lay back flat againstthe fuselage. As the nose of the aircraft pushes through a hole in thenet the rods 351 are forced back into their retracted position againstthe fuselage and then pop back up where they prevent the aircraft fromsliding back out of the net. Other approaches are of course possiblesuch as a claw that closes and grabs a line in the net in the samemanner as a train coupling.

It is understood that the UAV can engage the tow line 4 directly or canengage one or more other arrestment lines such as 20 and 21 as shown inFIG. 5 and in more detail in FIG. 6 hanging down from the tow line 4directly or hanging down from a beam mounted on the tow line 4.

The kinetic energy of the UAV during an arrestment is dissipatedprimarily through aerodynamic drag of the parachute 8 and tow line 4,mechanical friction on the tow line 4, drag from the winch as it reelsout the tow line and gravity with the amounts varying based on whicharrestment approach is used. Arrestments can be made with the vehicleintersecting the tow line 4 or secondary arrestment lines 20, 21approximately perpendicular (which is the preferred approach) orapproximately parallel or somewhere in between.

Flight paths 52 in FIGS. 5 and 54 in FIG. 8 are examples of intersectingthe arresting cables at an intermediate angle. An engagement usingflight path 52 as shown from the side in FIG. 5 and flight path 40 asseen from above in FIG. 8 represents what will be called a co-incidentengagement where the aircraft is flying level and in the same directionof travel as the parasail 8 and overtaking the parasail 8 and tow line 4from the rear.

Referring to FIG. 5, flight path 43 achieves a perpendicular engagementby doing a pull up or sustained climb prior to engagement. If a pull-upis used, the pilot might time the maneuver for example by using theforward looking camera to fly at a point 60 marked on the tow line 4such as with a strobe or flag until another point 62 is at the top ofhis video screen at which point he would do a pull-up to intersect thetow line 4 just below point 62 or some other marked spot on the tow line4.

A perpendicular engagement can also be achieved with a level flight pathin a number of different ways.

The preferred approach is to fly into engagement at right angles to thedirection of travel of the parasail using flight path 38 and eitherengaging the tow line 4 directly or lines hanging off the tow line 4. Itis also understood that the aircraft could engage lines hanging directlybelow the parasail.

In a second approach, prior to engagement the winch can be released sothe cable plays out very rapidly and the tow line 4 hangs near verticalbelow the parachute. The UAV 10 then engages the cable from anydirection and swings up on the cable and the winch then takes up theslack.

Modern winches can reel in at high speeds. The approach of letting thetow line go slack prior to the arrestment leads to very low loads andlong arrestment distances. Also modern parasailing winches willautomatically reel out at a pre-set braking force if the load in the towline 4 exceeds the pre-set force level. This also will reduce the loadsand absorb some of the arrestment energy. This pre-set braking force canbe lowered enough so that the tow line is playing out prior to thearrestment. This can steady the arrestment cables or net so it is notaffected as much by the heaving of the ship. Alternatively, the winch 6can also eliminate the movement of the arrestment point due to theheaving of the ship by reeling in and out to compensate to make thepilots job easier. The winch could be operated in this manner manuallyor automatically for example with the control system obtaining feedbackfrom an accelerometer hung on the tow line 4 and trying to minimize theaccelerations sensed by the accelerometer parallel to the tow line 4.Alternatively, the accelerometers could be located at the net orrecovery lines to directly sense any accelerations and activate thewinch or vary the lift and drag of the parasail to minimize thoseaccelerations.

For a heavy UAV, line 25, as seen in FIGS. 5 and 6, can be disconnectedfrom tow line 4 at point 47 and taken by a crew member inside the hangarand attached to a winch so the UAV 51 can be winched into the hangar orout for launch without even touching down on the flight deck. This ispossible because the UAV would still be suspended from line 21 on oneside and line 25 inside the hangar. For a small boat, line 25 could beused to pull the UAV forward to the back of the boat before it wouldotherwise land in the water behind the ship. An alternative to this isto have a winch at the top of line 20 or 21 where it attaches to towline 4 that could retract line 20 or 21 and pull the aircraft up to thetow line 4. An additional alternative is to replace the winch with apulley and have line 20 or 21 pass through the pulley and then extenddown the tow line so that personnel on the flight deck can grab the endof the line and pull the aircraft up to the tow line 4 before it mightcontact the water behind the ship.

Flight paths 46, 48 and 50 as shown in FIG. 5 are examples where the UAVintersects the tow line 4 at a near parallel angle which is not apreferred approach in that it generally requires greater piloting skilland makes for a poorer energy absorption approach. The preferredapproach when using this flight path is the approach previouslydescribed where the UAV drops a line that engages a grappling hook onthe tow line 4.

FIGS. 14A and 14B show UAV configurations designed to intercept thearresting cable at a near parallel angle. The UAV configuration of FIG.14A is designed so the wing would deflect any cables to the centerlinelatching mechanism that it flies up into or alternatively the landinggear struts would deflect any cables to the centerline latchingmechanism that the UAV flies down onto or vice versa if the vehicle wereflown upside down for engagement. The UAV of FIG. 14B is designed todeflect a cable to a centerline latching mechanism with its lower wingor its V tail surfaces. Other configurations are of course possible, forexample, the cables could be deflected to wingtip latches, dedicateddeflecting structures could be used, etc.

There are several approaches to prevent the UAV from sliding all the waydown the tow line 4 or sliding down and off the secondary arrestmentcables 20, 21.

The first approach is to have the inner throat of the latching hook 26as shown in FIG. 3 smaller than the diameter of the tow line 4 so as togenerate a sufficient amount of braking force. In addition, the throatof the latching hook could be spring loaded closed to provide aconsistent clamping and thus braking load on the tow line 4 independentof tow line 4 diameter. Another approach is to have the diameter of thetow line 4 equal to or smaller than the throat of the latching hook 26at the point of engagement so that the initial braking force is theco-efficient of friction times the normal force of the line pullingagainst the hook but the line would increase in diameter as the UAVslides down the line resulting in a slowly increasing braking force.Significant braking can still occur even though the tow line 4 issmaller in diameter than the throat of the latching hook 26 especiallyas the UAV and the latching hook 26 turns or the UAV hangs from the towline 4 so it is not lined up perfectly with the tow line 4 which mustthen snake through the hook causing drag.

Also as the UAV slides down the tow line 4 there is aerodynamic dragfrom the forward motion of the ship and the slope of the tow line 4 getsshallower as the UAV gets closer to the ship especially if there isn't alarge amount of tension on the tow line 4, so the UAV naturally slowsdown. The captain can also slow down the boat even to the point that thetow line 4 goes horizontal or sloping back up as the UAV slides down thetow line 4 toward the boat. Tourist parasail operators have such goodcontrol that they often bring the parasail rider down and get only hisfeet wet before raising him back up again.

Another approach is to have a fixed or sliding stop on the tow line 4which could also be padded to reduce any shock loads as the UAV contactsthe stop. A sliding stop could be designed to provide a fixed amount ofclamping or braking force on the tow line 4 or might be attached by aline to a small parachute to provide all or part of the braking force ormight just be a padded compressible material wrapped around the bottom30 feet of the tow line 4 to cushion any remaining downward velocity ofthe UAV.

For the preferred configuration where the secondary arrestment cables20, 21 are used the UAV cannot slide off the bottom of the cables due tocable 25 connecting the two at the bottom and in addition rigid stopsmay be placed on the line such as knots in the line that are too largeto pass through the throat of the latching hook. The cables 20, 21 atthe top end would preferably be attached to tow line 4 as shown in FIG.6 through a sliding attachment which like a sliding stop is designed tobrake against tow line 4 and absorb any kinetic energy parallel to thedirection of travel of the tow line 4. Lines 21, 20 and 25 attach toline 200 which assures the proper spacing between these three lines attheir upper ends. Line 200 in turn is attached to tow line 4 with ringcaribeaners 202 that can slide along tow line 4. To hold this assemblyof lines as shown and prevent it from sliding down the tow line, brakingmechanism 204 is provided which work like pliers and encircle the towline 4 like clothes pins. To attach the braking mechanism 206 to the towline the two handles 208 are spread so that the jaws of the device openenough to be placed around the tow line 4. The handles are then releasedand springs 206 act to pull the two handles of the braking mechanism 204together causing the jaws to trap and clamp down on the tow line 4. Arod 210 connects the braking mechanism 204 to the adjacent ringcaribeaner 202 and hold the braking mechanism 204 in the proper positionat right angles to the tow line 4 for a consistent braking force. Thepreferred arrestment flight path for this system is shown by flight path38 in FIG. 8. However if the UAV 51 engages lines 20 or 21 with too higha component of velocity parallel to the tow line 4 such as with flightpath 54 as shown in FIG. 8 then braking mechanism 204 slides along thetow line 4 absorbing this energy and preventing peak loads that mightdamage the UAV or the arrestment system.

It is understood of course that there could be more than just the twoarrestment lines 20, 21. Also in FIG. 7 is an alternate approach wherearrestment lines 212 are strung between tow line 4 above and line 214below. The primary difference in this configuration is that the tensionin the arrestment lines 212 are maintained by small weights 220 whichhold line 214 down and taut whereas line 25 was held down and taut byparachute 53. Also instead of braking mechanisms 204, bungee cords 390hold the net in place lengthwise along the tow line and reduce any shockloads parallel to the tow line. FIG. 29 shows a further alternateapproach where a single arrestment line 121 is suspended from a bungeecord 391 that spans along a section of tow line 4. It is held adjacentto the tow line by caribeaners 202′. Braking mechanisms 208′ may besimilarly employed to provide an arrestment load to the recovered UAV.In this fashion, a supplemented arrestment load is imparted to the UAVupon engagement with arrestment line 121 by the combination of thebungee cord 391 and braking mechanism 208′.

The altitude of the parasail can be varied dramatically as is known inthe art which can place the arrestment location at different altitudesto avoid ground fog at lower altitudes on one day or a low cloud coveron other days.

Net Enveloping Approach

If a manufacturer or user of a UAV wasn't willing to modify his UAV withthe mechanisms just described such as latching hooks 26 then it would benecessary to offer a net system such as shown in FIG. 17. Net 100 ishung from tow line 4 as seen in this isometric view and the UAV uses alateral flight path such as 38 to intercept the net 100 at near rightangles at the center 101 of the net. The very open mesh doesn't let theUAV pass through but lets the UAV's nose penetrate into one of theholes. Preferably the aircraft would be flown in a sideslip to eliminateany crabbing angle relative to the net to make sure the aircraft nosepenetrated straight into a hole of the net. A cable 102 is attached at104 and 106 to the left upper and left lower end of net 100. Likewisecable 108 is attached at 110 and 112 to the upper and lower right cornerof net 100. Net 100 itself consists of cables 350, 352, 354 and 356which comprise the four sides of the net and lines 360 which run up anddown and side to side and form the meshing between the sides of the net100. Lines 360 are firmly tied to each other where they cross in themiddle of the net and are also attached to the sides of the net 350,352, 354, 356 but by loops 370 that are capable of sliding along thesides of the net 350, 352, 354, 356. Velcro break-away straps 380 ateach corner of the net however tend to hold lines 360 and loops 370 intheir proper position as shown in FIG. 17 prior to an engagement.

Cables 102 and 108 pass loosely through low friction Teflon loops 120and 122 which also acts as a quick disconnect interface to tow line 4.Cables 102 and 108 can easily slide in loops 120 and 122 and these loops120 and 122 can also slide along tow line 4 but with a moderate level offriction with a device not shown but similar to the braking mechanism204 described previously. Small weights 107 and small parachutes 109 areattached to the lower left 106 and right 112 corners of the net 100 soas to provide a retarding force on the lower corners of the net similarto the restraint provided by tow line 4 to the upper corners 104 and110. From the UAV engagement, the net 100 is driven laterally away fromthe tow line and into a position shown in the middle of FIG. 18 wherethe net 100 has encapsulated the UAV 124. FIG. 19 shows the system afraction of a second later when the Velcro brake away straps 380 releasecausing the mouth of the net 130 to shut behind the UAV like thetie-wraps on a garbage bag. In a few more seconds the system ends uphanging from the tow line 4 as shown in FIG. 20.

The positive encapsulation of the UAV 124 is achieved because only thenet 100 blocks the flight of the UAV 124 and the net 100 is restrainedby lines 102 and 108 attaching at four points around the periphery ofthe net pulling the sides of the net all around the UAV 124 and alsobecause of the closing mouth of the net 100 similar to the tie-wraps ona garbage bag.

Overloading the tow line 4 or the parachute during an arrestment is nota problem for this invention because they would be over-designed for theloads in the same manner as current parasailing equipment. Theparachutes typically have 16 risers with each riser capable of anapproximate 900 lb. load. The load on the tow line is typically around900 lbs. but is typically capable of carrying 6 or 7000 lbs. Theparachute movement in response to loads also provides a very large shockabsorbing capability and modern winches on the ship can be set toautomatically play out when loads exceed a certain set amount. Prior tothe arrestment the parasail only needs to hold up the ballast so theload on the cable can be very low and still maintain a constant parasailaltitude and a low load setting can be selected for the winch which willkeep the load in the cable down during the arrestment. For current fixedgeometry parasails this requires that the relative wind at the parasailis low which means the ship must slow down or the winch can be playingout before the engagement with the UAV. After the arrestment the shipwould speed up or the winch play out load setting would be restored to ahigher value to stop the playing out of the tow line 4 and provide morerelative parasail airspeed to support the weight of the UAV. Whenperpendicular arrestments are used such as flight path 38, thearrestment loads will also go down the longer the length of the tow line4 connecting the ship and the parasail since this results in longer UAVarrestment distances.

Most ships wishing to operate UAVs are orders of magnitude larger thanparasail boats and much less maneuverable and responsive and also don'twant to have to slow down, speed up or change direction if possible inorder to launch or recover a UAV. As a result, it would be advantageousto have a variable geometry parasail that could increase or decrease itslift and drag independent of relative airspeed. It is believed that thiscan best be achieved using a variation on a technique used for slowingdown the opening of a parachute for load control.

FIG. 25A shows a parasail 244 that is fully inflated. Remote controlunit 230 contains a winch that can reel in or out lines 232 and 234which in turn pass back and up to the left and right rim of the parasailcanopy. Line 232 passes through a pulley and then passes up around themouth of the parasail canopy through rings 206 attached to each riserand line 234 passes down around the mouth of the parasail canopy. Byreeling in lines 232 and 234, remote control unit 230 can close down theparasail mouth such as shown in FIG. 25B in order to reduce the lift anddrag of the parasail. This technique is very effective and can greatlyreduce the load on the parasail and tow lines. This system has theadvantage that the ship can now operate over a much wider speed rangewithout worrying about either having too little parasail lift or toomuch load or drag on the system. Also only one parasail size is requiredto launch and recover different sized UAVs or carry various sizepayloads aloft. After a UAV launch the parasail lift and drag can bereduced to make it easier to pull back down. This system also allowsinflation of very large parasails on the flight deck in high winds in asafer more controlled manner by starting with the mouth of the parasail236 mostly closed down but the parasail lifted into the air by smallerparasail 240 pulling on and lifting line 242 which passes through and isattached to the center of the parachute at 246. Also after the parasailhas been winched back down onto the flight deck this system provides oneof the best approaches for deflating the parasail in high winds bytotally closing off the mouth 236. A small winch in remote control unit230 can let out line 242 so that parachute 240 will pull back at thecenter of the parasail 244 at point 246 to further deflate the chute,pull the parasail fabric back in a streamlined manner and keep theparasail material from flapping excessively or getting tangled. With anautomated approach the parasail risers and parasail 244 can be retractedall the way onto the winch 6 used to extend and retract the tow line 4.For launching parasail 240 would be deployed in a conventional mannerand it would pull the much larger parasail 244 off of the winch 6.

Parasail 244 would also be steerable as is known in the art forparatroop parachutes and remote control unit 230 would have smallwinches that pull left and right control lines in place of having aparatrooper doing it to keep the parasail in the correct rolled attitudeto provide lift vertically. This eliminates the need for ballast whichwould also make it very difficult to roll the parasail 244 onto thewinch 6. Without any ballast required only a very small amount ofrelative wind would be required to keep the parasail aloft betweenlaunches or recoveries. If a lighter than air and preferably a hot airballoon were integrated with this system then the ship could go for longperiods and operate in absolute zero relative wind conditions withouthaving to reel the system back in. It is also understood that inaddition or as an alternative to closing down the mouth of a parasailthat the lift and drag of the parasail 244 can be varied by pulling orreleasing symmetrically the control lines for the steerable parasailwhich results in symmetrically opening or closing the parasail controlvents which is known in the art. Alternatively, a separate vent in theparasail could be opened to lower its drag characteristics using asimilar system to that used for the steering vents or similar to thatshown in FIG. 25A to close down the mouth of the parasail. Still anotheralternative is shown in FIG. 25C. In this configuration remote controlunit 230 pulls on line 248 which passes through pulleys 250 and 252 atthe bottom and top of the parasail canopy rim. By pulling in line 248remote control unit 230 can pull the top and bottom of the canopy rimtogether in the middle and partially close down the parasail mouth andreduce the parasail drag.

Another approach to keeping a large towed deployable lifting system upall the time to avoid frequent inflation and deflation and not restrictthe direction and speed of the ship is to use a parafoil system steeredby a remote control unit which pulls control lines which is known in theart. In low or zero relative wind conditions the system would be unableto launch or recover a UAV but an electric motor driving a propellercould be powered through the tow line 4 to propel the parafoil to flyback and forth or in circles just fast enough to keep the system in theair.

A way to move the tow line 4 over the flight deck for launch andrecovery of UAVs but get it out of the way for recovery of a mannedhelicopter is to utilize the winds by proper orientation and cruisingspeed of the ship or use a steerable parasail, parafoil or otherdeployable lifting system to fly the tow line 4 left or right and/ordown to get it out of the way with the tow line attach point to the shipat a forward left or right corner of the flight deck 7.

Another less automated approach for deflating a large parasail is shownin FIG. 2 where hook 19 is attached to an aircraft tie down point on theflight deck and winch 6 lets out tow line 4 so that line 18 pulls on thebottom center of the canopy rim at point 37 but the remainder of theriser lines go limp so the parachute collapses.

In order for the ship to properly communicate with and control the UAVit generally needs line of sight communications. As a result, if the UAVflies low or gets too far away an airborne communications relay isrequired. Instead of launching a second UAV, the parasail can performthis function for the ship operating just like an airborne relay withits own power source etc. or by carrying antennas aloft and receivingthe signal and/or power through the tow line 4. The parasail can alsocarry its own sensors such as radar, TV or infrared sensors to providelocal area surveillance or decoy transmitters to draw incoming missilesaway from the ship. As a local area surveillance platform it might beespecially advantageous to use a steerable parachute as previouslydescribed so that the sensors for example could be steered directly overor to the back side of an object of interest close by the ship.

The release structure housing this electronic gear would be designed tobe buoyant and water-tight in case it accidentally landed in the waterand might even have a catamaran or other stable boat hull so that itcould also act as a towed water decoy for the ship when there isinadequate relative wind to keep it in the air. For use as a water bornedecoy the parasail would be removed or the release structure would haveto hold the parasail 8 risers high enough to keep the parasail fromdipping into the water. This electronic equipment would be carried wherethe water ballast 9 is shown in either FIGS. 1 or 2 and the weight ofthis electronic equipment would generally be large enough to satisfy therequirement for ballast and eliminate the need for the previouslydescribed water ballast 9. Any antennas would generally be hung on thetow line or the parasail risers of the parasail. The parasail rig couldalso be used to carry a man aloft and then release him with a steerableparachute either for pilot training on how to ditch into the water or toallow a soldier to parasail onto the shore or onto another ship, etc.With a remote control steering mechanism it could also be used in anunmanned application to deliver supplies. For some applications it willbe desirable to have a multi-color highly visible parasail for exampleto make it easier for the UAV to find the arrestment gear however formany military applications it may be more desirable that the parasail isdifficult to see by an adversary. In the latter case a transparentparasail material can be used such as that used for weather balloons ora gray parasail as is common for this purpose since it blends so wellwith various sky colors.

Although the preferred approach to hold up the lines to engage the UAVfor arrestment is to use a deployable lifting surface such as a parasailit should also be understood that the aircraft could latch onto linessuspended between poles mounted in the ground as shown in FIG. 21. Forexample the same techniques described previously to engage the slantedparasail tow line 4 or lines 20, 21 could be used to engage slanted guyline 74 or vertical lines 76 in FIG. 21. Line 74 is an example wherestops are not used while lines 76 are shown with stops 81 to prevent theUAV from sliding down the lines. These stops 81 for example can consistsimply of a knot in the line with or without a washer resting on top ofit or it could consist of a ring around the line that squeezes down onthe line to generate friction to hold it in place or to slide along theline with energy absorbing drag. The energy absorbing mechanisms forthis deck mounted system are flexible supporting posts 78 which can bendwithout breaking and the elasticity inherent in the lines 74, 76.

As an additional different embodiment, arrestment lines could besuspended from the end of a rotating arm attached to the superstructureof a ship. FIGS. 27 and 28 show an example of a rotating arm extendingfrom a ship for suspending the recovery system. Beam 600 is attached tothe side of the ship's hangar 602 from a rotating base 604. A line 606controls the horizontal movement of beam 600 from an aft position to aposition extending laterally from the ship as shown in FIG. 28 and aline 607 supports the beam 600 and controls the vertical movement of thebeam. A winch 609 can reel in or out line 607 in order to raise or lowerthe boom and by alternately reeling in and out can take out the effectof the rolling of the ship in heavy seas. The winch 609 can becontrolled manually to perform this function or can be performed by anautomatic system that for example measures the slope of the beam anddrives the winch 609 to for example keep the beam level as the shiprolls. Arrestment lines 608 and 610 are suspended from the beam 600 attheir upper end and connect down to an arrestment engine 612 which isknown in the art as a way to absorb energy for net or cable recoverysystems. Some of these arrestment engines use a paddle in a drum ofwater, and they would allow lines 608 and 610 to be pulled off of a reelwith a braking force.

The aircraft 616 is flown into and engages vertically hung arrestmentlines 608 and/or 610 as previously described while flying in the samedirection as the ship and the ship is preferably oriented directing intothe wind. Beam 600 would be oriented in a laterally extending positionin relation to the ship. The aircraft 616 may be guided by its internalcamera or a centerline camera 614 on the boom 600 can also be used bythe pilot to steer the aircraft in. After the aircraft 616 engages thecables 608 and/or 610 the boom 600 swings forward as the aircraft 616 isslowed to a stop. Stops, as described above, are placed on the lines608, 610 to prevent the aircraft 616 from falling into the water afterthe arrestment. Line 606 is then manipulated so that boom 600 can berotated over the flight deck 618 so that the aircraft 616 can beretrieved from the recovery system.

A different approach is required for land based launch and recoverysince you don't always have the relative wind of a ship based system.One land based approach is to use a helicopter as shown in FIG. 22.Prior to flying on a mission an external load line 132 is attached tothe bottom of one of the helicopters 130 in an attack group which has arelease mechanism 134 and UAV 136 attached to the other end. Thehelicopter 130 carries the UAV 136 to altitude where it is released bythe release mechanism 134 and launched as described previously for theparafoil system. The UAV 136 could of course also be carried to altitudefor launch under one of the helicopters pylons as also shown in FIG. 22.After launching all the UAVs the helicopter drops the line 132, andrelease mechanism 134 back at the home field. The UAV 136 then flies outwith the helicopter 130 to perform a mission where it flies high to findand designate targets while the manned helicopter 130 can stay hiddenbelow the tree line and pop up only to fire its missiles at the targetsdesignated by the UAV 136. When the helicopter 130 returns home theexternal load line 132 and release mechanism 134 or a separate load linewithout the release mechanism are again attached to the helicopter 130which carries it aloft. The UAV 138 returning at the end of the missionthen engages the vertical hanging cable as previously described and islowered to the ground. The UAV 138 at engagement is not flying that muchfaster than the helicopter or the line 132 is long enough and the UAV138 engages the line low enough that the UAV 138 will never swing up tothe level of the helicopter 130. The pilot controlling the UAV 138 coulduse the UAV's thrust and directional control with the propellerslipstream blowing over the rudder and horizontal tail to steer the UAV138 to the best landing location while hanging below the helicopter 130and keep from getting under the helicopter downwash by staying out infront.

For large UAVs or landing on the ground it is more critical that the UAV138 be hanging perfectly upright so it lands on its wheels and not forexample a wing. FIG. 23 shows a mechanism that makes this possible withthe pre-engagement position shown in solid and the post-engagementposition shown in dashed lines. UAV 138 is shown with the wing 140 in anoblique position as described earlier to deflect the vertically hangingcable 132 laterally into engagement with latching hook 142 which isintegrated into the end of wing leading edge arm 144 which is shownshaded in the figure and forms the leading edge of the wing section overthe fuselage and lays flat and aerodynamically blended along the top ofthe wing as shown with one hinge point 146 on the front of the wing'sfront spar and one hinge point 148 on the back of the back wing spar fora strong, lightweight and aerodynamic design. The load from line 132during the engagement lifts the latching hook 142 and attached arm 144to the vertical position shown in dashed lines where it can't rotate anyfurther due to rods 150 and 152 which can lock arm 144 in position andprovide a connection at 154 to the wing's front spar and at 156 to thearm 144 just below the latching hook 142. With this approach the UAV 138is now suspended by the cable 132 at a point substantially over thecenter of gravity so that it will land on its landing gear. Beforeengagement, rods 150 and 152 are folded up and streamlined underneatharm 144 and in front of the wing torque box structure. Latching hook 142or an attach point on arm 144 near latching hook 142 can be used toattach the load line 132 and raise the UAV 138 for launch and atrelease, arm 144 is spring loaded by springs 151 and 153 to go back toits down, streamlined position (shown in shaded, solid lines). Iflatching hook 142 is used as the attach point then an actuator in thelatching hook 142 and controlled by the UAV can be used to retract thelatching mechanism for release during the launch.

Alternatively rods 150 and 152 can be deleted from the design whicheliminates the restraining mechanism for arm 144 which allows the UAV tochange and control its pitch attitude while hanging on cable 132 usingits propeller wash blowing over elevators 143. This alternative approachcan be advantageous for launch since the UAV can hold itself in a noseup attitude where the thrust from the UAVs engine can assist in raisingthe aircraft. For landing by holding the aircraft level in pitch theaircraft will also be level in roll independent of the exact sweptposition of the wing 140.

During an arrestment, arm 144 will swing almost 180 degrees about hingepoints 146 and 148 to lay over the aft swept wing 140. The load from thearrestment can then be used to rotate the wing 140 to a more highlyswept position over the fuselage if this is desirable such as to avoidcontact with the ground or other objects on landing and reduce anydownload from the helicopter downwash that might also try to overturnthe UAV 138.

Another approach for land based use is to use lighter than air such ashelium or hot air as the lifting system. A lighter than air approachgets very large however unless it is used in combination with a parasailtype system so the lighter than air lift required is only enough to getthe parasail and tow line 4 aloft in zero wind conditions. FIG. 24 showsone such approach where the lighter than air balloon and liftingparasail are integrated together. There are risers 61 that hold theballoon down and are essentially always taut and there are risers 63that are attached to parasail fabric 68 which in turn is attached aroundthe sides of the balloon 64 and surround risers 61. In a no windcondition risers 63 and attached parasail fabric material 68 is limp asshown in solid lines and cross-checked area in FIG. 24. With a relativewind the parasail inflates quickly to the position shown in dashed linesbecause risers 61 inside of the parasail fabric act to hold open themouth of the canopy so it will capture air. The balloon 64 is biasedwith more volume and thus more lift forward of the center of theparachute, parasail or parafoil which in a wind helps keeps therotational position of the parasail about its symmetrical axis orientedwith the forward end up to provide lift pointed upward in a similarmanner to how the ballast is used with a conventional parasail to keepit properly oriented. The balloon 64 thus provides the lift to get theparasail airborne but also helps to properly orient it and hold itpartially open so that it will rapidly fully inflate under a load or awind. Balloon 64 could have vertical tail fins 66 to keep the balloonoriented into the wind but preferably would just have aft biased panelson the parasail to provide this function as is known in the art.

A tether line 82 connects to the bottom of the balloon 64 and parachute68 system which in turn is attached to the ground or even hand held orfor a large system a winch 84 for retracting the system down through theopen roof of trailer 86 for transporting the system. Part way up theline is air inflated cushion 88. For an arrestment the roof of thetransporter is opened and the balloon 64 is allowed to rise to a pointabove any obstructions such as trees 90. UAV 80 flies into and engagestether line 82 below balloon 64 and above cushion 88. It should beunderstood that any of the alternative flight path and engagement meanspreviously described for the pure parasail system also apply for thisland based hybrid system. Due to the wind if any and the translationalspeed after UAV 80 engagement, the parachute material 68 deflects outand inflates providing the primary source of lift and drag of the systemto slow the translational speed of the UAV 80 and provide a low descentrate. The UAV 80 slides down the cable 82 until it rests on top of aircushion 88 which is large enough to cover the entire underside of theUAV 80 and cushion the impact with the ground. After the UAV 80 lands onthe ground the lighter than air balloon 64 keeps the parachute up out ofthe bushes. However one preferred approach is not to land on the groundat all but to have the winch reel the UAV in as it is descending to landon the floor of the trailer whose side-walls might fold down to be outof the way during the landing. With this approach air cushion 88 mightstill be used for the case when the winch 84 might fail or could bereplaced with a very large air cushion on the floor of the trailer. Thedrum for winch 84 runs the length of the trailer 86 so that the risers61 and 63 and parasail fabric 68 can also be wound up on the drum andballoon 64 can be rapidly drawn back down into the trailer fortransportation. The winch also might be powered by a drive shaft fromthe vehicles main transportation engine.

It is also understood that instead of a lighter than air element to keepthe parasail aloft in zero wind conditions electric power could beprovided through the cable 82 to power an electric motor that drives apropeller that flies the parasail or parafoil back and forth or in acircle until the engagement.

1. An aerial recovery system for an aircraft, said system comprising; anarrestment line held up at at least one end, said aircraft containing adevice for capturing said line, said aircraft containing structuresuitable for deflecting said line laterally into engagement with saidcapturing device, said structure comprising a wing of said aircraft. 2.The aerial recovery system of claim 1 where said line is held up by alifting apparatus.
 3. The aerial recovery system of claim 1 where saidcapturing device is a hook.
 4. The aerial recovery system of claim 3where said hook has a line retaining device.
 5. The aerial recoverysystem of claim 1 in which said capturing device is positioned on aforward inboard edge of a wing of said aircraft.
 6. The aerial recoverysystem of claim 1 in which the capturing device is located inboard ofthe aircraft's wingtip.
 7. The aerial recovery system of claim 6 inwhich the capturing device is located inboard more than 5% of the wingsemi-span.
 8. The aerial recovery system of claim 1 in which multiplegenerally vertically oriented arrestment lines are spaced apart acrossthe direction of travel of said aircraft as it approaches for recoveryso as to increase the lateral capture envelope of said recovery system.9. The method for recovering an aircraft of claim 1 in which said lineis deflected inboard relative to the aircraft.
 10. The aerial recoverysystem of claim 1 in which said line is supported in the air by a rotor.11. The aerial recovery system of claim 1 in which said line issupported in the air by an aircraft.
 12. The recovery system of claim 1wherein the arrestment line is held up by a device selected from thegroup consisting of a balloon, an aircraft, a lifting device requiring arelative wind to generate lift, and a beam.
 13. The recovery system ofclaim 12 where said arrestment line is held up by a beam, the beamcomprising a boom.
 14. A method for capturing a flying object,comprising the steps of: a) suspending a linear or curvilinear fixtureacross the flight path of the object in a generally verticalorientation, or otherwise in an orientation which includes a componentnormal to the flight path; b) guiding the object to strike the fixture;c) allowing the subsequent motion of the object to slide the fixturealong a wing or spanwise lifting surface of the flying object; d)intercepting the sliding of the fixture by one or more hooks attached toa wing or spanwise lifting surface of the flying object; e) deceleratingthe flying object under the restraint of the fixture; and f) removingthe flying object from the fixture.
 15. An aerial recovery system for aheavier-than-air aircraft, said system comprising, the aircraft; and anarrestment line held up at at least one end, said aircraft comprising acapturing device for capturing said line and structure suitable fordeflecting said line laterally into engagement with said capturingdevice.
 16. The aerial recovery system of claim 15 wherein saidstructure is constructed to deflect said line laterally outboard. 17.The aerial recovery system of claim 15 wherein said arrestment line isheld up by a beam.
 18. In combination, a flying object and an apparatusfor capturing the flying object, the flying object having a spanwiselifting surface with a capture device, the flying object being adaptedfor flying along a flight path, the apparatus comprising: a generallylinear or curvilinear fixture positionable in the flight path of theflying object, at least a portion of the fixture being inclined at anangle relative to the spanwise lifting surface to intersect the spanwiselifting surface, the fixture having an engaging surface positioned toengage the capture device of the flying object to releasably secure theflying object to the fixture; and a support structure coupled to thefixture and positioned to support the fixture in the flight path. 19.The combination of claim 18 wherein the fixture includes a cable orpole.
 20. The combination of claim 18 wherein the support structureincludes a lifting device requiring a relative wind to generate lift, aballoon, an aircraft, and a beam.
 21. The combination of claim 18wherein the capture device comprises at least one hook on the spanwiselifting surface of the flying object.
 22. The combination of claim 21wherein the at least one hook includes a latch.
 23. The combination ofclaim 22 wherein the fixture includes a cable or pole and wherein thesupport structure includes a lifting device requiring a relative wind togenerate lift, a balloon, an aircraft, or a beam.
 24. The combination ofclaim 21 wherein the fixture includes a cable or pole and wherein thesupport structure includes a lifting device requiring a relative wind togenerate lift, a balloon, an aircraft, or a beam.
 25. A method forcapturing a flying object comprising: allowing a spanwise liftingsurface of a flying object to strike a fixture positioned at an anglerelative to the spanwise lifting surface while imparting a deceleratingforce to the flying object; releasably engaging the fixture with acapture device on the flying object; and retrieving the flying object.26. The method of claim 25 further comprising sliding at least one ofthe spanwise lifting surface and the fixture relative to the other whilethe fixture contacts the spanwise lifting surface.
 27. The method ofclaim 25 further comprising selecting the fixture to include at leastone of a cable and a pole.
 28. The method of claim 25 whereinpositioning the fixture comprises suspending the fixture from at leastone of a lifting device requiring a relative wind to generate lift, aballoon, an aircraft, and a beam.
 29. The method of claim 28 furthercomprising selecting the fixture to include at least one of a cable anda pole, and wherein releasably engaging the fixture with the capturedevice comprises engaging the fixture with at least one hook on asurface of the flying object.
 30. The method of claim 29 furthercomprising selecting the at least one hook to include a latch.
 31. Themethod of claim 25 wherein releasably engaging the fixture with capturedevice comprises engaging the fixture with at least one hook on asurface of the flying object.
 32. The method of claim 25 furthercomprising orienting the fixture at an angle approximately normal to thespanwise lifting surface.
 33. The method of claim 25 wherein the fixtureis operatively coupled to a floating object, and wherein the methodfurther comprises bringing the flying object aboard the floating object.34. In combination, a flying object and an apparatus for capturing theflying object, the combination comprising: a) a linear or curvilinearfixture suspended across the flight path of the object in a generallyvertical orientation, or otherwise in an orientation which includes acomponent normal to the flight path; b) means for suspending thefixture; and c) means attached to the flying object for intercepting thesliding of the fixture along a wing or spanwise lifting surface of theflying object.
 35. The combination of claim 34, wherein the linear orcurvilinear fixture is a cable.
 36. The combination of claim 34, whereinthe means for suspending the fixture is selected from the groupconsisting of a kite, a balloon, a kite/balloon hybrid, an aircraft, amast, and a crane.
 37. The combination of claim 34, wherein the meansfor intercepting the sliding of the fixture comprises at least one hookon a wing or spanwise surface of the flying object.
 38. The combinationof claim 34, wherein each hook includes a cleat or latch such that afterthe fixture is intercepted by the hook, sliding of the fixture throughthe hook is substantially arrested.
 39. The combination of claim 34,wherein the motion of the flying object during deceleration isaccommodated by compliance of the fixture.
 40. A method for capturing aflying object, comprising the steps of: a) suspending a linear orcurvilinear fixture across the flight path of the object in a generallyvertical orientation, or otherwise in an orientation which includes acomponent normal to the flight path, such that the suspension of thefixture is kept clear of said flight path by a distance greater than theheight or width of said flying object; b) guiding the object to strikesaid fixture; c) intercepting the fixture by one or more hooks attachedto a wing or spanwise lifting surface of the flying object; d)decelerating the flying object under the restraint of the fixture; ande) removing the flying object from the fixture.
 41. In combination, aflying object and an apparatus for capturing the flying object, thecombination comprising: a) means for suspending a linear or curvilinearfixture across the flight path of the object in a generally verticalorientation, or otherwise in an orientation which includes a componentnormal to the flight path, such that the suspension of the fixture iskept clear of said flight path by a distance greater than the height orwidth of said flying object; b) means for suspending the fixture; and c)means attached to a wing or spanwise lifting surface of the flyingobject for intercepting the fixture.
 42. The combination of claim 41,wherein the fixture is a cable.
 43. The combination of claim 41, whereinthe means for suspending the fixture is selected from the groupconsisting of a kite, a balloon, a kite/balloon hybrid, an aircraft, amast, and a crane.
 44. The combination of claim 41, wherein the meansfor intercepting the fixture comprises at least one hook on a wing orspanwise surface of the flying object.
 45. The combination of claim 41,wherein each hook includes a cleat or latch such that after the fixtureis intercepted by the hook, sliding of the fixture through the hook issubstantially arrested.
 46. The combination of claim 41, wherein themotion of the flying object during deceleration is accommodated bycompliance of the fixture.